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Emerging Bio-Precursors for Chemical Processes

Abstract

Dacryodes edulis (G. Don) H.J. Lam resin was hydro-distilled to recover essential oil (EO), and further purified to produce a heavy fraction constituting less volatile compounds. Chemical composition was investigated by gas chromatography-mass spectrometry (GC-MS), and indicated that different monoterpenes and triterpenes were present depending on the analyzed fraction. Bioassays were performed on the different fractions to evaluate their anti-fungal and anti-termite properties. Results indicated that crude resin, its heavy fraction and its EO all had proved termicidal properties, which decrease on drying for EO and crude resin due to evaporation of monoterpenes. Conversely, no anti-fungal properties were observed for any fraction. Dacryodes edulis resin is therefore a new valuable bioactive ingredient for the formulation of wood protection products with anti-termite properties.

Abstract

Previously, it was reported that plant protoplasts isolated from Betula platyphylla (white birch) callus secreted bundles of hollow callose fibrils in acidic culture medium containing a high concentration of calcium ions (Ca2+). Here, the callose synthase was characterized from in situ and in vitro perspectives. Localization of callose synthases at the secreting site of callose fiber was indicated from in situ immunostaining observation of protoplasts. For in vitro analyses, membrane proteins were extracted from membrane fraction of protoplasts with a 3-[(3-cholamidopropyl)-dimethylammonio]-1-propanesulfonate (CHAPS) treatment. The CHAPS extract aggregated in the presence of a high concentration of Ca2+, suggesting that Ca2+ may promote the arrangement of callose synthases in the plasma membrane. The callose synthase activity was dependent on pH and Ca2+, similar to the callose synthase of Arabidopsis thaliana. However, the synthesized fibril products were longer than those produced by callose synthases of herbaceous plants. This is the first insight into the specific properties of callose synthases of woody plants that secrete of callose hollow fibers.

Abstract

To analyze the chemical composition and evaluate the potential commercial value of Dalbergia odorifera leaves, the chemical component and content of the essential oils (EOs), fatty acids (FAs), polyphenols and flavonoids in the leaves of D. odorifera were studied. The composition of the EOs obtained by simultaneous distillation extraction (SDE) (at the yield of 0.092%) and hydro-distillation (HD) (at the yield of 0.050%) from D. odorifera leaves was analyzed by gas chromatography-mass spectrometry (GC-MS). Seventy-six compounds were identified and the major compounds were phytol (22.5–24.3%), 4-vinylguaiacol (8.7–12.7%), dihydroedulan II (7.4–11.2%), γ-elemene (5.1–6.2%), cedrol (2.8–6.1%), coumaran (0.9–3.1%) and hexahydrofarnesyl acetone (2.5–2.7%). The FA yield extracted by ultrasound was 1.145% (w/w), and the most abundant FA components were palmitic acid (C16:0), oleic acid (C18:1) and linoleic acid (C18:2) in leaves. The results of the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis (3-ethylbenzothiazoli-ne-6-sulfonic acid (ABTS+) radical scavenging experiments demonstrated that the EOs and FAs possess strong antioxidant activity. The ethanol extract of the leaves had a high polyphenol content [16.00 mg gallic acid equivalent (GAE) g−1 dry weight (DW)] and flavonoid content [8.92 mg rutin equivalent (RE) g−1 DW]. This research has determined qualitatively and quantitatively the isoflavonoids (biochanin A, isoliquiritigenin, tectorigenin and genistein) by ultra-performance liquid chromatography-electrospray ionization-tandem mass spectrometry (UPLC-ESI-MS/MS). The phytochemical analysis (EOs, FAs and flavonoids) of the extract showed that the D. odorifera leaf is a rich source of high bioactive compounds and might have the potential to be recommended for further cosmetics, food and pharmaceutical applications.

Abstract

To understand the reasons for the high durability of tropical wood species, the chemistry of the extractives needs to be elucidated. As these extractives consist of a great variety of components differing in quantity and composition, the analysis is often time-consuming. To focus on the key bioactive substances, bioassay-guided fractionation is helpful, but the established bioassay methods cannot be readily adapted to basidiomycete fungi that are commonly used for the respective durability tests, because they do not sporulate easily in laboratory settings. The research therefore aims at developing a direct bioautography using homogenized hyphae from basidiomycetes, to overcome this restriction. Extracts from four tropical wood species were analyzed regarding their potential bioactivity on two selected basidiomycete fungi. To this end, the chemically complex mixtures and extract constituents were resolved by a two-dimensional planar chromatography and the metabolites were located by characteristic zones of fungal growth inhibition, which was accentuated by a color reaction. The bioactive fractions were analyzed by gas chromatography/mass spectrometry (GC/MS). Potentially responsible compounds could be identified, such as the alkaloid bicuculline from Mezilaurus itauba, which has not been described in this species yet. The presented bioassay method can be used as a rapid screening method for bioactive components from wood.

Abstract

Heat treatment (HT) is thought to degrade wood surface wettability and cause gluing problems; this study focused on wettability and surface strength of the surface layer on heat-treated wood. The outer and inner surfaces formed by removing the 1-, 2- and 3-mm surface layers of heat-treated poplar on the tangential section were investigated. Dynamic wetting was analyzed according to the sessile drop method. The bonding failure models on different surfaces were also discussed based on both images of macro- and microscopic fracture interfaces. Using Fourier-transform near-infrared spectroscopy (FT-NIR), the cell wall chemistry on both outer and inner surfaces were analyzed. The results showed that the bonding strength of the outer surface was mainly affected by wettability, whereas the surface strength became the key factor for the inner layers. The removal of the first 1 mm of the surface layer enhanced the wetting process and transferred the failure mode from the glue line to the wood itself. FT-NIR revealed that the intensity of the thermal degradation on inner layers was alleviated with the removal depth; wettability and surface strength were enhanced compared with the outer surface. Surface abrasion and hardness declined, decreasing the surface strength and bonding capacity. This study indicates that the bonding of heat-treated wood is truly affected by the surface strength of the inner layers, in addition to the wettability on the outer surface.

Abstract

Wood is a renewable natural lignocellulosic material. However, its hygroexpansion characteristics dramatically shorten its service life, and limit its application. In this study, wood was treated in a silicone oil bath at different temperatures to improve its dimensional stability. Results demonstrated that the silicone oil treatment decreased the tangential swelling coefficient by 13% when treated at 80 °C and by 34% when treated at 160 °C and the radial swelling coefficient by 12% when treated at 80 °C and by 49% when treated at 160 °C. Also, the moisture absorption was reduced by the treatment.

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Abstract

To understand the irreversible dimensional changes caused by hygrothermal treatment of green wood, i.e. hygrothermal recovery (HTR), green hinoki compression wood (CW) and normal wood (NW) were hygrothermally (HT) treated in water at 100°C for 120 min and their HTR strains were determined. The specimens were then swollen using dimethyl sulfoxide (DMSO) and then completely dried after solvent exchange with water at room temperature. Their HTR strains were then compared with their DMSO swelling and drying shrinkage strains. The volumetric HTR strains in the CW were about twice as large as those in the NW. Moreover, the microfibril angle (MFA) was found to be an important factor for controlling the HTR intensity. A clear commonality between the HTR behavior and both DMSO swelling and drying shrinkage behavior was identified, which indicates that HTR is caused by volumetric changes in the matrix substances. HTR has been defined as a phenomenon due to the release of locked-in growth stress when a wood specimen is HT treated. To determine whether DMSO treatment has a similar effect as hygrothermal treatment, both HT-untreated and HT-treated specimens were swollen using DMSO, and their dimensional changes during and after DMSO treatment were compared. The results showed that DMSO treatment is a possible alternative for releasing the locked-in growth stress.